The present invention relates generally to a mechanical grip device powered by an ultrasonic motor, particularly useful as a prosthetic hand.
There are an estimated 100,000 individuals with the loss of arms or hands in the United States alone and as many as 10,000 new amputees each year. Research has been carried out in the area of providing prosthetic limbs for many years. The result of this research has provided complex multiple degrees-of-freedom hands, which are too large and complex to be feasible in the marketplace. In contrast, a number of more commercially viable and affordable one-degree-of-freedom hands have been created. These prosthetic hands are combined with powered prosthetic elbows. The hands and elbows are driven by small electric motors. Command signals to drive the powered motors are provided by electrodes which receive electrical signals from the amputee""s remaining muscles.
The practical one-degree-of-freedom prosthetic hands or gripping devices that have become commercially available have a number of shortfalls. One of these problems is the weight of the prosthetic hands. Prosthetic hands on the market, which have a relatively high gripping force, weigh more than 16 ounces. This weight is due, in part, to the weight of the electromagnetic motors and gear reductions used. For hands weighing less than 13 ounces, the strength of the grip is cut in half because the size and strength of the motor. are reduced.
It is a significant problem in a prosthesis to provide a small a high torque motor. This is because the motor must be small enough to fit within the envelope of the amputee""s limb that is being replaced. In industrial and scientific robotic applications, torque is increased by increasing the motor size or increasing the electrical power delivered to the motor. This is not possible in prosthetics because an increase in motor size increases the weight of the prosthesis an amputee must constantly carry and it is not aesthetically pleasing. A larger motor results in the motor protruding from the prosthetic limb. Furthermore, increasing the power delivered to the motor is not possible in a prosthesis because the power source must be portable and must remain small. Accordingly, it would be valuable to have a motor for use in a prosthesis which provides a high torque output without increasing the motor size or power requirements.
It has been recognized that it would be advantageous to develop a system to provide a prosthesis with a mechanical power source which reduces the weight of the prosthesis, runs more quietly, provides a more direct drive, and has low power consumption.
In accordance with one aspect of the present invention, a movable prosthetic limb includes a drive linkage, which is configured to move the prosthetic limb. An ultrasonic drive motor is coupled to the drive linkage and powers the drive linkage. The ultrasonic motor is non-backdrivable and has high torque at low speeds. Specifically, a prosthetic limb can use an ultrasonic motor to drive a prosthetic elbow joint or prosthetic fingers.
In accordance with another aspect of the present invention, a movable prosthetic wrist includes a base configured to be coupled to an amputee. An ultrasonic drive motor is attached to the base, and a hand piece is attached to the ultrasonic drive motor to form a prosthetic wrist joint. In this configuration, the ultrasonic drive motor directly moves the prosthetic wrist joint. A harmonic drive or eccentric gears can also be used for gear reduction in the prosthetic wrist joint.
Another important aspect of the present invention is a prosthetic gripping device having at least two opposable digits. A drive linkage is configured to enable the two opposable digits to grip. An ultrasonic drive motor is used to directly power the drive linkage.
Additional features and advantages of the invention will be set forth in the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate by way of example, the features of the invention.